Unisex clothing for a teenager would be sweat pants, hoodies, and, as said above, hanes t-shirts. Sometimes we buy t-shirts from our school with our school logo on it, and those are obviously considered unisex.
I’m not sure on “dressy” unisex clothing though.

@Samant BTW, Welcome to Fluther. I hope you find the community here fun.

I guess lots of things qualify. Jeans, simple t-shorts and tank tops, jogging pants, Bermuda shorts, lots of sports paraphernalia like sweat shirts, tees, baseball caps and the like are sized differently for men and women, but cut about the same. Shirts that button up would be unisex except that we have a silly convention that men’s shirts have the buttons on the right and holes on the left. Shirts designed for women have the opposite arrangement.

As @Simone_De_Beauvoir noted, though, you’d end up with a pretty restrictive wardroab for male or female going that route.

@Samant I’ve always gotten mine in the men’s dept. They shrink to fit, so they pretty much fit everybody and look good on both males or females. I think the ones that are similar, but specifically for women might not be 501’s, they might have a differnt number.